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Number of molecules or atoms in a given mass or number of moles

This type of question, asked 5 times: 26 Apr 2025 S2, 18 Apr 2026 S2, 20 Apr 2026 S2, 13 May 2026 S1, 13 May 2026 S2. All 5 questions below, oldest first.

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  1. Question 1

    26 Apr 2025 S2

    51
    Calculate number of molecules present in 5.4 g of urea (Molar mass of urea =60 g mol−1= 60\text{ }g{\text{ }mol}^{- 1} ).

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  2. Question 2

    18 Apr 2026 S2

    1
    Find the number of molecules present in 70 g dinitrogen.

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  3. Question 3

    20 Apr 2026 S2

    1
    What is the number of molecules in 2.125 g of ammonia?

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  4. Question 4

    13 May 2026 S1

    1
    Calculate the number of molecules in 22 mol of MgO.

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  5. Question 5

    13 May 2026 S2

    1
    Calculate the number of atoms in each of the following. (a) 11.211.2 g nitrogen (b) 1.151.15 g sodium

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